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741.
M. Morini D. Maccagni L. Maraschi D. Molteni E. G. Tanzi A. Treves 《Space Science Reviews》1985,40(3-4):601-606
We have observed the BL Lac object PKS 2155-304 with the EXOSAT observatory and with IUE on 1983 October 31 and November 29. At the same time, optical photometry has been obtained. Variability has been observed both on a time scale of hours during the October 31 observation and on the time scale of one month. During the November 29 observation the source was 2 times brighter than in the previous observation, but no spectral modification is found between the two observations. The source has been also detected in the ME instrument and an energy spectrum has been fitted with a power law. A marginal detection in the ME Xenon counters suggests a flattening of the spectrum in the high energy band. These X-ray data extending over three decades in energy are compared with the simultaneous UV and optical observations. 相似文献
742.
Ph. Rebillard P.N. Pascaud D. Sarrat 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(11):133-138
Synthetic Aperture Radar data were acquired over Tunisia by Seasat in Aug. 1978 and by SIR-A in Nov. 1981. The radar images are contrasted to the Landsat scenes overlapping the same area. The Landsat images were taken in Aug. 1978 and in Sept. 1981. In this study, subareas of the SIR-A and MSS images are registered to the corresponding Seasat data (1313 lines by 1970 samples). The test site is located East of Kairouan, Tunisia. It is a low relief area with subdesertic climatic conditions. This region was selected for it has been surveyed by both Seasat and SIR-A providing perpendicular radar illumination directions. The multispectral and multitemporal coregistered data set enables comparisons between the systems (radar versus MSS, and Seasat versus SIR-A), and change detection in the desertification processes and on the surface of the playas. 相似文献
743.
Ts. Pasheva D. Samardziev N.P. Benkova N.A. Kochenova Ju. Kushnerevskij 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(1):61-64
In this paper, combined bottom- and topside ionospheric N(h)-profiles are presented for the Bulgarian region. The profiles were constructed using ground (ionospheric observatories Sofia and Michurin) and satellite (Interkosmos-19) observations /1/.The observatories make quarter-hourly observations; in order to connect bottom and upper parts of the N(h) profile, we selected satellite orbits passing rather near to the observatory (zenith distance lsss than 100 km). Thus the time difference between ground station and satellite measurement was never more than 7.5 min. 相似文献
744.
R. J. Hung Y. D. Tsao B. B. Hong F. W. Leslie 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1988,8(12):205-213
Time dependent evolutions of the profile of free surface (bubble shapes) for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry, have been studied. Numerical computations of the dynamics of bubble shapes have been carried out with the following situations: (1) linear functions of spin-up and spin-down in low and microgravity environments, (2) step functions of spin-up and spin-down in a low gravity environment, and (3) sinusoidal function oscillation of gravity environment in high and low rotating cylinder speeds. The initial condition of bubble profiles was adopted from the steady-state formulations in which the computer algorithms have been developed by Hung and Leslie/1/, and Hung et al./2/ 相似文献
745.
D R Morrison M L Lewis G H Barlow P Todd M E Kunze B E Sarnoff Z Li 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(5):77-79
Suspensions of cultured primary human embryonic kidney cells were subjected to continuous flow electrophoresis on Space Shuttle flight STS-8. The objectives of the experiments were to obtain electrophoretically separated fractions of the original cell populations and to test these fractions for the amount and kind of urokinase (a kidney plasminogen activator that is used medically for digesting blood clots), the morphologies of cells in the individual fractions, and their cellular electrophoretic mobilities after separation and subsequent proliferation. Individual fractions were successfully cultured after return from orbit, and they were found to differ substantially from one another and from the starting sample with respect to all of these properties. 相似文献
746.
Statistical and operational results of extensive government field-testing of the Rockwell-Collins Global Positioning System (GPS) units are summarized. The equipment has exhibited better than 16-m spherical-error probable-position accuracy in over 6300 hours of testing conducted during the past two years. One-channel, two-channel, and five-channel receivers were subjected to thorough evaluation. Their respective signal-processing and data-processing architectures are described. Data highlighting dynamic position accuracy, static position accuracy, acquisition times, and field reliability are presented. GPS equipment integration and operation with nine different host vehicles is described. The results of mission scenarios, such as area navigation, rendezvous, and weapon delivery, are presented 相似文献
747.
Artur D. Chernin 《Space Science Reviews》1995,74(3-4):447-454
George Gamow (1904–1968) was a man with boundless interests and imagination that took him from relativity theory to quantum mechanics and nuclear physics, back to cosmology and then to genetics. He had made seminal contributions to these key areas of modern knowledge which ensured him an enduring place among the giants of twentieth-century science. 相似文献
748.
A. Léger J. -J. Puget J. M. Mariotti D. Rouan J. Schneider 《Space Science Reviews》1995,74(1-2):163-169
We report the concept of an IR observatory, with interferometric rejection, to search for Primitive Life on an extra-Solar Planet which has been proposed to the European Space Agency. 相似文献
749.
This paper analyzes a buck/boost regulator employing current-injected control (CIC). It reveals the complex interactions between the dc loop and the current-injected loop and underlines the fundamental principle that governs the loop gain determination. Three commonly used compensation techniques are compared. The integral and lead/lag compensation are shown to be most desirable for performance optimization and stability. 相似文献
750.
D. Winske 《Space Science Reviews》1985,42(1-2):53-66
Hybrid codes in which part of the plasma is represented as particles and the rest as a fluid are discussed. In the past few
years such codes with particle ions and massless, fluid electrons have been applied to space plasmas, especially to collisionless
shocks. All of these simulation codes are one-dimensional and similar in structure, except for how the field equations are
solved. We describe in detail the various approaches that are used (resistive Ohm's law, predictor-corrector, Hamiltonian)
and compare results from the various codes with examples taken from collisionless shocks and low frequency wave phenomena
upstream of shocks. 相似文献